Tomatoes not flowering or producing

Question

I planted 15 tomato plant of different varieties on May 30th. There was excessive heat and humidity in the Washington DC area, above 90 degrees in July and August. I tilled the ground with composted horse manure and used granular fertilizer a few times. The Husky Cherry tomatoes have plenty of flowers and tomatoes are growing and turning red every day but not the other varieties like, Roma, ‘Bonnie’ Better boy, Big boy and Celebrity. It is now September and I do not have many tomatoes growing on the other varieties. I may have used too much nitrogen? Or the excessive heat and humidity has caused the flowering to halt or pause https://www.thespruce.com/tomato-blossom-drop-1402964. Is anyone in this area having the same problems with their tomatoes? In just the past week the weather has cooled into the 80’s. And I now see more flowering and tomatoes are growing, plus there is more wind. I read the wind helps with pollinating and flowering. I have also been using Tomato blossom set spray. I went to Butler’s Orchard https://www.butlersorchard.com/ in Gaithersburg Maryland on 9/10 and their tomato plants are full of green tomatoes, it looks like they may be turning red in about 4 weeks. Their cinnamon apple pie is amazing!

Answer 1

It could very well be the heat and humidity, but there are a few other options as well--what comes to mind first for me is that May 30 is a little late to transplant out tomato plants--usually I transplant around May 1 or even a little earlier (into unheated high tunnels in southern Michigan), so in DC the tomato season could start even earlier than that. Looks like your last frost date is around the end of March, so with a couple pieces of row cover (Agribon or similar) on hand for any unseasonably cold nights, you could definitely get your tomatoes in the ground earlier next year for an earlier harvest, say early to mid-April, depending on if it's a warm spring or not.

By transplanting earlier the plants get an earlier start on growing and producing fruit, and the plant gets a chance to grow nice and big and robust before it starts to set flowers--the bigger the plant before it sets flowers, the more nutrition there is available to help the fruit grow and ripen. Some people even prune off the first one or two flowering branches of their plants to let the plant really bulk up before letting it start growing fruit.

Depending on variety there are 20-50 days of ripening time between flower set and the fruit being ripe, so depending on when your tomatoes set flowers, yours could be right on schedule according to their internal clocks!

Without knowing what kind of fertilizer you added I can't say if it's a problem of too much nitrogen or not (although that can certainly affect fruit set), but from the photos you shared it doesn't look to be the case. Usually plants with too much N are super lush and green and full of bigger-than-usual leaves, and yours don't look to be suffering from N overdose to me. Probably what you added was a good amount.

There are other nutrients that can affect flower set/fruit set, among them potassium and calcium. Here's a good general sheet about potassium's role in tomato growth: https://www.yara.us/crop-nutrition/tomato/role-of-potassium/ And here's a short overview of calcium's: https://sustainablefarming.com.au/wp-content/uploads/2019/03/Organic-Ca-Tomatoes-SFS-Technical.pdf

There's also the watering schedule--tomatoes seem to do best for me with a consistent schedule of a little water every day, so that they always have moisture around their roots and therefore the plants are able to access all the water-soluble nutrients and micronutrients whenever they need them. On hotter days they need more water, because the plant transpires more to help keep itself cool. I don't know what kind of watering setup you've got, but this one (https://www.veggiegardener.com/threads/watering-tomatoes-using-a-2-liter-soda-bottle.1886/) is a great free option for tomatoes.

The ground cover you have over them is also really good idea--that really helps them to preserve moisture, although during the heat of the summer I would either change it out for a white plastic one, or just cover the black plastic with some hay or straw, to help keep the soil around the roots cool--excess heat in the soil can also be stressful to the plant especially with the temps we've had.

Good luck with your tomatoes, looks like they're coming along well--you should be able to harvest quite a few. If you want your plants to concentrate their energy on ripening the fruits that are full-size, you can prune the top 6-12 inches off the plants. They will stop growing and producing flowers (more or less, except for the cherry tomato varieties) and put their energy into ripening the fruits that they already have. The plants will keep growing and producing as long as the nighttime temps stay consistently above 50 degrees F, (and as long as they don't succumb to diseases), and when it gets too cold you can harvest the green, blemish-free tomatoes, remove the stem, and lay them out on a piece of cardboard upside-down, in a sunny window, and the tomatoes will continue to ripen slowly over the next few weeks. They won't be as delicious as the ones you pick ripe off the vine, but hey, a fresh, home-grown tomato in December is still better than one from the grocery store!

Answer 2

It looks like you're square foot gardening. With that in mind, I'm guessing the real problem is one of these:

• The soil (the composition and the amount of it)
• The plants are too close together (except for the dwarf indeterminate cherry: Husky Cherry Red F1, which is a vareity known to do well in containers, which have limited soil). Yes, you can grow big tomatoes that way, and you are actually doing it (you do have some big fruits), but for ideal results, I'd recommend more space between your plants for those varieties, unless you're willing to fertilize a lot.

Roma and Celebrity F1 can set fruit just fine in very hot temperatures (much better than many varieties and just as well, in my experience, as Husky Cherry Red F1); so, that's not the problem. Humidity with heat, maybe, but just heat, no. However, I've never heard of humidity causing plants to not flower before. I think that must have another cause (plants too close together is a common cause of reduced flowering/production; it's not so much that the roots are too close together that matters--although that does matter--as that the foliage is too close together; when tomato foliage is crowded, it often doesn't produce or flower/fruit as much). When roots are too close together, plants use up the nutrients very fast.

If you're going to amend the soil for better results, a soil test would probably be preferable, if you have the means to do so and don't mind dealing with that (it might be kind of expensive for an end-of-season thing, though). My guess, however, is that the plant needs the following nutrients to go along with all that nitrogen (if the nitrogen really is high, which I don't think is really the case):

• Calcium
• Phosphorus
• Potassium
• Possibly magnesium

Adding some monopotassium phosphate, garden gypsum, and Epsom salt would provide those nutrients. Dolomite lime has calcium and magnesium, but can raise the pH some. Wood ash has lots of calcium, as well as a vast array of micronutrients in smaller amounts, but it can raise the pH (with all that nitrogen, if it is high, you might have acidic soil, though). Gypsum is pH-neutral, though (which is why I mentioned it first).

It's a little late in the season to be worrying that much about fertilizer, though (unless the soil depth is limited, or you're using a container, that's mostly a first half of the season sort of thing), but phosphorus probably would help speed the ripening along, even if there's not time to get new fruits.

On the plus side, even if your fruits don't ripen in time, you can pick them and let them ripen the rest of the way indoors. It does work (and it even helps the seeds to mature, if you're a seed-saver). It's best to pick some stem with the fruit (instead of pulling the stem and calyx off).

Plants with lots of nitrogen tend to have glossier, shinier, more tender leaves. Nitrogen also helps a lot with making the leaves a nice green. I do see chlorosis in your plants, so it's possible you might have too little nitrogen (rather than too much); that could be caused by disease or another deficiency, however. Plants with low nitrogen can still have tender leaves, if they're also low in potassium.

I'm guessing fertilizer in general (not specifically what I mentioned in that list above) is probably what you need (but it's a little late, if your frost is coming up soon). Adding it probably won't hurt, though.

It does look like there is some disease, by the nectrotic parts of the yellowing leaves. I'm not sure what kind of disease (possibly more than one). Maybe a copper foliar spray would reduce the issue some (copper is antifungal and used for some tomato diseases). Copper probably wouldn't help with Verticillium, and viruses, though, as an antimicrobial (as a nutrient, it might help, if the plants need more). Fertilizer can improve results in the face of a number of diseases.

I think what you're doing is actually working pretty well.